THE ELECTRIC CURRENT. 23 



1 668. 6 grams of copper sulphate crystals are used. Find: (a) 

 The amount of copper sulphate crystals which is consumed by 

 voltaic action, and (b] the amount of copper sulphate crystals 

 which is consumed by local action. Ans. (a) 504.6 grams use- 

 fully consumed in voltaic action and (^) 1,164 grams wasted in 

 local action. 



Note. Copper sulphate crystals contain 12 molecules of water of crystallization, 

 that is to say, the formula for copper sulphate crystals is CuSO 4 -(- I2H.,O so that 

 375.9 grams of copper sulphate crystals contain 63.6 grams of copper. 



10. An ordinary dry cell was connected to a circuit, the cur- 

 rent at the start was 5.00 amperes, and the current was observed 

 at intervals of 10 minutes, giving the following values in amperes 

 in order: 4.20, 3.92, 3.70, 3.55, 3.40, 3.28, 3.16, 3.02, 2.90, 

 2.81, 2.72, 2.60, 2.54, 2.48, 2.43, 2.37, 2.30, 2.24, 2.16. Plota 

 curve of which the abscissas represent elapsed times and of which 

 the ordinates represent the decreasing values of the current deliv- 

 ered by this cell. 



11. A lead storage cell delivers 10 amperes for 8 hours. Find the increase of 

 weight of each electrode. Ans. The positive electrode or grid gains 95.5 grams, and 

 the negative grid gains 143.3 grams. 



12. The storage cell specified in problem II contains 4,000 cubic centimeters of 

 dilute sulphuric acid of which the density at 18 C. is 1.1700 grams per cubic centi- 

 meter when the cell is fully charged. Find the density of the electrolyte after the 

 cell has delivered 10 amperes for 8 hours. Ans. 1. 1286 grams per cubic centimeter. 



DATA REQUIRED IN THE ABOVE PROBLEMS. 

 ATOMIC WEIGHTS. 



Silver !O7.93 Sodium 2 3-S 



Aluminum 27.1 Oxygen 16.00 



Copper 63.6 Lead 206.91 



Iron 55-88 Sulphur 32.06 



Hydrogen i.oi Zinc 65.40 



Density of dry hydrogen at o C. and 760 mm. pressure, 0.0000896 gram per cubic 

 centimeter. 



Density of dry oxygen at o C. and 760 mm. pressure, 0.001429 gram per cubic 

 centimeter. 



